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LEGO Mindstorms NXT
- sensors and electronics
in NXT robots
Pavel Ripka, (modified by Vojtch Petrucha)
Department of Measurement, CTU in Prague
http://measure.feld.cvut.cz
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Sensors ?
Interface between a real world and
your control algorithms and artificialintelligence (robots)
A sensor is a device that measures a
physical quantity and converts it into a
signal which can be read by an
observer or by an instrument. (Wiki)a
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Whats this?
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1.5 2 billions US$ burning..
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B2 Spirit
Moisture in three of the 24 sensors that
feed information into the bombers
computer system caused the sensors to
send bad information about the planes
speed and altitude, and howfar up or
down the bombers nose was pointed.
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NXT brick
http://mindstorms.leg
o.com/Overvie
w/NXTreme.aspxhttp://www.jstuber.net/lego/nxt-programming/nxt-top_big.jpg
Main processor: Atmel 32-bit AR
M
processor, AT91SAM7S256
- 256 KB FLASH
- 64 KB RAM
- 48 MHz
Co-processor: Atmel 8-bit AVR
processor, ATmega48
- 4 KB FLASH
- 512 Byte RAM
- 8 MHz
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4input ports
1: analog input 10-bit ADC 0..5 V+ current generator (back compatibility with RCX)
2, 3: GND
4: + 4,3 V 5,6: digital I-O, I2C bus (Inter-Integrated Circuit)
(only the ultrasonic sensor uses it from the basic set..)
I2C half-duplex communication,
START,ADDRESS,ACKNOWLEDGE, DATA , STOP
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3 output ports
1-2 PWM outputs for motors (or programmable voltage 0..5 V) 3 GND
4 power supply 4,3 V
5,6 Schmitt inputs (e.g. for IRC sensor - encoder)
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Touch sensor
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measures level of soundmagnitude acoustic pressure
0 dB you can here it..
120 (130) dB level of pain
Microphone
A5M02AKA Akustick aplikace
dBa .... physiological correction
it shows percents [%] of90 dB
4-5% silent room
5-10% far conversation
10-30% normal conversation
30-100% screaming or noisy music
20 dB = one order increase
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Ultrasonic range-meter
measures distance 0 (?) to 255 centimeters with a resolution
+/- 3 cm.
principle: time offlight
piezoelectric transmitter and receiver(separated)
speed ofsound 346 m/s (changing with
temperature, pressure)
good reflection is needed
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Motor and IRC sensor
If you use the Move block in the LEGO
MINDSTORMSNXT software to program your
motors, the two motors will automatically
synchronize, so that your robot will move in a
straight line.
Rotation Sensor measures motor rotations in
degrees or full rotations [accuracy of +/- one
degree].
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motor characteristics
http://www.philohome.com/motors/motorcomp.htm
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How you can
measure the
torque
http://www.philohome.com/motors/motorcomp.htm
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Motor efficiency
A3B14EPR Elektrick pohony pro automatizaci a robotiku
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Overload protection ofNXT motor
current through braked motor: 2 A,
momentum 50N.cm
in-build PTC thermistor over-voltage diode (D4) .. both polarities 15 V
http://www.philohome.com/motors/motorcomp.htm
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Motor control H bridge
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IRC sensor
- like in a computer mouse
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counts on rising and falling edges (direction and resolution)
Non-magnetic platform, also contains IRCs. Code-wheel made ofPCB, no
ferromagnetic components..
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Simple I2C interface
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Connection ofDACand VCO for RC servo
http://www.extremenxt.com/tda8444.html
A3M38ZDS Zpracovn a digitalizace analogovch signl
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Communication
Bluetooth wireless communication
CSR BlueCoreTM 4 v2.0 +EDR System
1 master + max. 3 slave
USB 2.0 communication Full speed port
12 Mbit/s
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USB connection Control Transfer
Isochronous Transfer
Interrupt Transfer
Bulk Transfer
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BluetoothBluetooth wireless
communication CSR
BlueCoreTM 4 v2.0
+EDR System
-Supporting the Serial
Port Profile (SPP)
- Internal 47 KByte RAM
- External 8 MBit FLASH
- 26 MHz
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LCD display control
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Sound output channel with 8-bit resolution
- Supporting a sample rate of2-16 KHz
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Battery6 AA cells or Li-Ion accu
reversible fuse 1,85 A (disconnects at about 3,3 A
5 V stab. 3,3 V stab. for ARM7 a Bluecore
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Other sensors forNXT
Infrared range-meter (triangulation)
20 150 cm, resolution mmConnection I2C
Sharp GP2Y0A02YK sensor
http://www.mindsensors.com
http://www.eduxe.cz/legomenu/hitechnic_menu.htm
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detektor
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Compass
Ourwo
rk..
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Digital Camera
Ourwork
Where we teach it..: A3M38VBM L
Videometrie a bezkontaktn men
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Accelerometer
mindsensors
hitechnic
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Gyro
http://web.mac.com/ryo_watanabe
video http://www.youtube.com/watch?v=V40ScvJeFxg
Prezentace NTXway-G
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Gyroscope
(iMEMS by Analog Devices)
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Real operation
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Pressure
http://www.extremenxt.com/pressure.htm
mindsensors
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Other applications
RFID reader http://www.norgesgade14.dk/rfid.phpMicroprocesor communicates with NXT using I2C
HiTechnic Products http://www.hitechnic.com
Codatex RFID sensor http://www.codatex.com